Materials for organic electroluminescent devices

ABSTRACT

The present invention relates to fluorene derivatives and to electronic devices in which these compounds are used as matrix material in the emitting layer and/or as hole-transport material and/or as electron-blocking or exciton-blocking material and/or as electron-transport material.

The present invention relates to organic semiconductors and to the usethereof in electronic devices, in particular in organicelectroluminescent devices.

Organic semiconductors are being developed for a number of differentelectronic applications. The structure of organic electroluminescentdevices (OLEDs) in which these organic semiconductors are employed asfunctional materials is described, for example, in U.S. Pat. Nos.4,539,507, 5,151,629, EP 0676461 and WO 98/27136. However, furtherimprovements are still desirable for use of these devices forhigh-quality and long-lived displays. Thus, there is currently still aneed for improvement, in particular, in the lifetime and efficiency ofblue-emitting organic electroluminescent devices. Furthermore, it isnecessary for the compounds to have high thermal stability and a highglass-transition temperature and to be sublimable without decomposition.In particular for use at elevated temperature, a high glass-transitiontemperature is essential for achieving long lifetimes.

There therefore continues to be a demand for improved materials, forexample host materials for fluorescent and phosphorescent emitters, butfurther improvements are also desirable, in particular, incharge-transport materials, i.e. hole- and electron-transport materials,charge-blocking materials and exciton-blocking materials. The propertiesof these materials in particular are frequently limiting for thelifetime and efficiency of the organic electroluminescent device.

Surprisingly, it has been found that the combination of substituted9,9-diarylfluorenes with nitrogen-containing 6-membered heteroaromaticgroups, in particular triazine, enables high efficiencies and longlifetimes to be achieved.

The present invention therefore relates to these compounds and to theuse thereof in electronic devices, in particular in organicelectroluminescent devices. Depending on the substitution, the compoundsaccording to the invention are suitable, in particular, as matrixmaterials for fluorescent or phosphorescent compounds, exciton-blockingmaterials, hole-blocking materials and electron-transport materials. Thematerials according to the invention enable an increase in theefficiency with the same or improved lifetime of the electronic devicecompared with materials in accordance with the prior art. Furthermore,these compounds have high thermal stability. In general, these materialsare very highly suitable for use in electronic devices since they have ahigh glass-transition temperature. The corresponding extendedstructures, in particular indenofluorene structures and indenocarbazolestructures, likewise have very good properties. The good solubility andgood film-formation properties make the compounds also particularlysuitable for processing from solution.

The invention thus relates to compounds of the formula (1)

where the following applies to the symbols and indices used:

-   Y is a single covalent bond, C(R¹)₂, CO, O, S, SO, SO₂, NR³, PR³ or    P(O)R³;-   X is on each occurrence, identically or differently, CR¹ or N, where    a maximum of three groups X in each ring stand for N;-   A is on each occurrence, identically or differently, CR² or N, where    a maximum of three groups A in each ring stand for N;-   R¹, R² are on each occurrence, identically or differently, H, D, F,    Cl, Br, I, CN, NO₂, N(R⁴)₃, Si(R⁴)₃, B(OR⁴)₂, C(═O)R⁴, P(═O)(R⁴)₂,    S(═O)R⁴, S(═O)₂R⁴, —CR⁴═CR⁴—, OS₂R⁴, a straight-chain alkyl, alkoxy    or thioalkoxy group having 1 to 40 C atoms or a branched or cyclic    alkyl, alkoxy or thioalkoxy group having 3 to 40 C atoms or an    alkenyl or alkynyl group having 2 to 40 C atoms, each of which may    be substituted by one or more radicals R⁴, where one or more    non-adjacent CH₂ groups may be replaced by R⁴C═CR⁴, C≡C, Si(R⁴)₂,    Ge(R⁴)₂, Sn(R⁴)₂, C═O, C═S, C═Se, C═NR⁴, P(═O)(R⁴), SO, SO₂, NR⁴, O,    S or CONR⁴ and where one or more H atoms may be replaced by D, F,    Cl, Br, I, CN or NO₂, or an aromatic or heteroaromatic ring system    having 5 to 60 aromatic ring atoms, which may in each case be    substituted by one or more radicals R⁴, or an aryloxy or    heteroaryloxy group having 5 to 60 aromatic ring atoms, which may be    substituted by one or more radicals R⁴, or aralkyl or heteroaralkyl    group having 5 to 60 aromatic ring atoms, which may be substituted    by one or more radicals R⁴; two or more adjacent substituents R¹    together with the atoms to which they are bonded or two or more    adjacent substituents R² together with the atoms to which they are    bonded may also form a mono- or polycyclic, aliphatic or aromatic    ring system with one another;    -   characterised in that at least one substituent R¹ which is        bonded to X stands for triazine, which may be substituted by one        or more radicals R⁴,    -   or in that at least one substituent R² stands for a 6-membered        heteroaromatic group, which may be substituted by one or more        radicals R⁴, and at least one radical R¹ simultaneously stands        for an aromatic or heteroaromatic ring system having 5 to 60        aromatic ring atoms, which may be substituted by one or more        radicals R⁴;-   R³ is on each occurrence, identically or differently, an aromatic or    heteroaromatic ring system having 5 to 60 ring atoms, which may in    each case be substituted by one or more radicals R⁴, or an aryloxy    or heteroaryloxy group having 5 to 60 aromatic ring atoms, which may    be substituted by one or more radicals R³, or a combination of these    systems;-   R⁴ is on each occurrence, identically or differently, H, D, F, Cl,    Br, I, CN, NO₂, N(R⁵)₃, Si(R⁵)₃, B(OR⁵)₂, C(═O)R⁵, P(═O)(R⁵)₂,    S(═O)R⁵, S(═O)₂R⁵, —CR⁵═CR⁵—, OS₂R⁵, a straight-chain alkyl, alkoxy    or thioalkoxy group having 1 to 40 C atoms or a branched or cyclic    alkyl, alkoxy or thioalkoxy group having 3 to 40 C atoms or an    alkenyl or alkynyl group having 2 to 40 C atoms, each of which may    be substituted by one or more radicals R⁵, where one or more    non-adjacent CH₂ groups may be replaced by R⁵C═CR⁵, C≡—C, Si(R⁵)₂,    Ge(R⁵)₂, Sn(R⁵)₂, C═O, C═S, C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O,    S or CONR⁵ and where one or more H atoms may be replaced by D, F,    Cl, Br, I, CN or NO₂, or an aromatic or heteroaromatic ring system    having 5 to 60 aromatic ring atoms, which may in each case be    substituted by one or more radicals R⁵, or an aryloxy or    heteroaryloxy group having 5 to 60 aromatic ring atoms, which may be    substituted by one or more radicals R⁵, or aralkyl or heteroaralkyl    group having 5 to 60 aromatic ring atoms, which may be substituted    by one or more radicals R⁵; two or more radicals R⁴ here may also    form a mono- or polycyclic, aliphatic or aromatic ring system with    one another together with the atoms to which they are bonded;-   R⁵ is on each occurrence, identically or differently, an aliphatic,    aromatic and/or heteroaromatic hydrocarbon radical having 1 to 20 C    atoms; two or more radicals R⁵ here may also form a mono- or    polycyclic, aliphatic or aromatic ring system with one another    together with the atoms to which they are bonded.

For clarity, the structure and numbering of 9,9-diphenylfluorene isdepicted below:

An aryl group in the sense of this invention contains 6 to 60 C atoms; aheteroaryl group in the sense of this invention contains 1 to 59 C atomsand at least one heteroatom, with the proviso that the sum of C atomsand heteroatoms is at least 5. The heteroatoms are preferably selectedfrom N, O and/or S. An aryl group or heteroaryl group here is taken tomean either a simple aromatic ring, i.e. benzene, or a simpleheteroaromatic ring, for example pyridine, pyrimidine, thiophene, etc.,or a condensed aryl or heteroaryl group, for example naphthalene,anthracene, pyrene, quinoline, isoquinoline, etc.

An aromatic ring system in the sense of this invention contains 6 to 60C atoms in the ring system. A heteroaromatic ring system in the sense ofthis invention contains 1 to 59 C atoms and at least one heteroatom inthe ring system, with the proviso that the sum of C atoms andheteroatoms is at least 5. The heteroatoms are preferably selected fromN, O and/or S. An aromatic or heteroaromatic ring system in the sense ofthis invention is intended to be taken to mean a system which does notnecessarily contain only aryl or heteroaryl groups, but instead inwhich, in addition, a plurality of aryl or heteroaryl groups may beinterrupted by a short non-aromatic unit (preferably less than 10% ofthe atoms other than H), such as, for example, an sp³-hybridised C, N orO atom. Thus, for example, systems such as 9,9′-spirobifluorene,9,9-diarylfluorene, triarylamine, diaryl ether, stilbene, benzophenone,etc., are also intended to be taken to be aromatic ring systems in thesense of this invention. An aromatic or heteroaromatic ring system islikewise taken to mean systems in which a plurality of aryl orheteroaryl groups are linked to one another by single bonds, for examplebiphenyl, terphenyl or bipyridine.

For the purposes of the present invention, a C₁- to C₄₀-alkyl group, inwhich, in addition, individual H atoms or CH₂ groups may be substitutedby the above-mentioned groups, is particularly preferably taken to meanthe radicals methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl,s-butyl, t-butyl, 2-methylbutyl, n-pentyl, s-pentyl, cyclopentyl,n-hexyl, cyclohexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl,2-ethylhexyl, trifluoromethyl, pentafluoro-ethyl and2,2,2-trifluoroethyl. An alkenyl group in the sense of this invention istaken to mean, in particular, ethenyl, propenyl, butenyl, pentenyl,cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenylor cyclooctenyl. An alkynyl group in the sense of this invention istaken to mean, in particular, ethynyl, propynyl, butynyl, pentynyl,hexynyl, heptynyl or octynyl. A C₁- to C₄₀-alkoxy group is particularlypreferably taken to mean methoxy, trifluoromethoxy, ethoxy, n-propoxy,i-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy or 2-methylbutoxy. Anaromatic or heteroaromatic ring system having 5-60 aromatic ring atoms,which may also in each case be substituted by the radicals R mentionedabove and which may be linked to the aromatic or heteroaromatic groupvia any desired positions, is taken to mean, in particular, groupsderived from benzene, naphthalene, anthracene, phenanthrene,benzophenanthrene, benz-anthracene, pyrene, chrysene, perylene,fluoranthene, naphthacene, pentacene, benzopyrene, biphenyl,biphenylene, terphenyl, terphenylene, fluorene, spirobifluorene,dihydrophenanthrene, dihydropyrene, tetrahydropyrene, cis- ortrans-indenofluorene, truxene, isotruxene, spiro-truxene,spiroisotruxene, furan, benzofuran, isobenzofuran, dibenzofuran,thiophene, benzothiophene, isobenzothiophene, dibenzothiophene, pyrrole,indole, isoindole, carbazole, pyridine, quinoline, isoquinoline,acridine, phenanthridine, benzo-5,6-quinoline, benzo-6,7-quinoline,benzo-7,8-quinoline, phenothiazine, phenoxazine, pyrazole, indazole,imidazole, benzimidazole, naphthimidazole, phenanthrimidazole,pyridimi-dazole, pyrazinimidazole, quinoxalinimidazole, oxazole,benzoxazole, naphthoxazole, anthroxazole, phenanthroxazole, isoxazole,1,2-thiazole, 1,3-thiazole, benzothiazole, pyridazine, benzopyridazine,pyrimidine, benzopyrimidine, quinoxaline, 1,5-diazaanthracene,2,7-diazapyrene, 2,3-diazapyrene, 1,6-diazapyrene, 1,8-diazapyrene,4,5-diazapyrene, 4,5,9,10-tetraazaperylene, pyrazine, phenazine,phenoxazine, phenothiazine, fluorubin, naphthyridine, azacarbazole,benzocarboline, phenan-throline, 1,2,3-triazole, 1,2,4-triazole,benzotriazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole,1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole,1,2,5-thiadiazole, 1,3,4-thiadiazole, 1,3,5-triazine, 1,2,4-triazine,1,2,3-triazine, tetrazole, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine,1,2,3,5-tetrazine, purine, pteridine, indolizine and benzothiadiazole.

In an embodiment, the compound of the formula (1) corresponds to acompound of the formula (2), (3), (4), (5), (6), (7), (8), (9), (10),(11), (12), (13), (14) or (15):

where the symbols and indices used have the meanings indicated above.

In the formulae (2) to (15), X preferably stands, identically ordifferently on each occurrence, for CR¹.

As already described above, the invention is characterised in that atleast one group R¹ stands for triazine or in that at least one group R²stands for a 6-membered heteroaromatic group and in that at the sametime at least one group R¹ stands for an aromatic or heteroaromatic ringsystem. These may each be substituted by one or more radicals R⁴.

If at least one group R¹ stands for triazine, this is preferably1,3,5-triazine or 1,2,4-triazine, particularly preferably1,3,5-triazine, which may in each case be substituted by one or moreradicals R⁴. The radicals R⁴ which are not equal to hydrogen ordeuterium preferably stand for an aromatic or heteroaromatic ringsystem, particularly preferably for phenyl, biphenyl, terphenyl orquaterphenyl.

If at least one group R² stands for a 6-membered heteroaromatic group,this is preferably selected from triazine, pyrimidine, pyrazine,pyridazine or pyridine, particularly preferably 1,3,5-triazine orpyrimidine, each of which may be substituted by one or more radicals R⁴.The radicals R⁴ which are not equal to hydrogen or deuterium preferablystand for an aromatic or heteroaromatic ring system, particularlypreferably for phenyl, biphenyl, terphenyl or quaterphenyl.

Particularly preferred triazine substituents R¹ and R² and pyrimidinesubstituents R² are the structures depicted below:

where the dashed bond indicates the link from this group to theskeleton.

In a further preferred embodiment of the invention, the compound of theformula (1) corresponds to the compound of the formula (16) or (17):

where the symbols and indices used have the meanings indicated above.

Particularly preferred structures for the compound of the formula (1)are compounds (18) to (27):

where the symbols and indices used have the meanings indicated above. Inthe formulae (24) and (25), the radical R¹, which is bonded to thecarbon bridge, i.e. to the group Y, is in each case, independently ofone another, preferably an aliphatic or aromatic hydrocarbon radical,particularly preferably methyl, ethyl, propyl or phenyl, where twophenyl groups may form a ring with one another and may thus form a spirosystem.

Further particularly preferred compounds are compounds (28) to (34)shown below:

where the symbols and indices used have the meanings indicated above. Incompound (33), the radicals R¹ are particularly preferably selected insuch a way that R¹ denotes an aromatic ring system and the radical R²contains a nitrogen-containing 6-membered heteroaromatic group, inparticular substituted or unsubstituted 1,3,5-triazine. Substituents onthe triazine are preferably aromatic groups.

Examples of preferred compounds of the formula (1) are structures (1) to(122) depicted below.

The compounds of the formula (1) according to the invention can beprepared by synthesis steps which are generally known to the personskilled in the art. The starting compound used for symmetricallysubstituted compounds according to the invention can be, for example,3,3′,5,5′-tetra-bromobenzophenone (Eur. J. Org. Chem. 2006, 2523-2529).This can be reacted, for example, in accordance with Scheme 1 with asubstituted or unsubstituted 2-lithiobiphenyl, 2-lithiodiphenyl ether,2-lithiodiphenyl thioether, 2-(2-lithiophenyl)-2-phenyl-1,3-dioxolane or2-lithiophenyldiphenylamine to give the corresponding triarylmethanols,which are then cyclised under acidic conditions, for example in thepresence of acetic acid and a mineral acid, such as hydrogen bromide.The organolithium compounds required for this reaction can be preparedby transmetallation of the corresponding aryl bromides (2-bromobiphenyl,2-bromodiphenyl ether, 2-bromodiphenyl thioether,2-(2-bromophenyl)-2-phenyl-1,3-dioxolane, 2-bromophenyldiphenylamine,etc.) using alkyllithium compounds, such as n-butyllithium. Analogously,it is possible to employ the corresponding Grignard compounds.

The tetrabromides produced in this way can be converted further bymethods known to the person skilled in the art. Palladium-catalysedreaction with boronic acids (Suzuki coupling) or with organozinccompounds (Negi-shi coupling) results in aromatic or heteroaromaticcompounds according to the invention (Scheme 2). At least one radical R²here contains a nitro-gen-containing 6-membered heterocycle, or at leastone Br is substituted by a group which contains a triazine group.

The invention furthermore relates to a process for the preparation ofthe compounds of the formula (1), comprising the reaction ofbis(3,5-dibromo)-benzophenone with a substituted or unsubstituted2-lithiobiphenyl, 2-lithiodiphenyl ether, 2-lithiodiphenyl thioether,2-(2-lithiophenyl)-2-phenyl-1,3-dioxolane, 2-lithiophenyldiphenylamineor a corresponding Grignard compound to give a triarylmethanol, followedby cyclisation under acidic conditions and optionally followed byfurther reaction of the bromine groups. At least one radical R² herecontains a nitrogen-containing 6-membered heterocycle, or at least oneBr is substituted by a group which contains a triazine group.

The compounds according to the invention described above, in particularcompounds which are substituted by reactive leaving groups, such asbromine, iodine, triflate, tosylate, boronic acid or boronic acid ester,can be used as monomers for the production of corresponding dimers,trimers, tetramers, pentamers, oligomers, polymers or as the core ofdendrimers. The oligomerisation or polymerisation here preferably takesplace via the halogen functionality or the boronic acid functionality.This applies, in particular, to compounds of the formulae (2) to (15) inwhich at least one radical R¹ or R², preferably two radicals R¹ and/orR², each stand(s) for a reactive leaving group, in particular selectedfrom the groups mentioned above.

The invention therefore furthermore relates to dimers, trimers,tetramers, pentamers, oligomers, polymers or dendrimers comprising oneor more compounds of the formula (1), where one or more radicals R¹ orR² or one or more H atoms of the compound of the formula (1) representbonds between the compounds of the formula (1) in the dimer, trimer,tetramer or pentamer or bonds from the compound of the formula (1) tothe polymer, oligomer or dendrimer.

An oligomer in the sense of this invention is taken to mean a compoundwhich has at least six units of the formula (1). A polymer in the senseof this invention is taken to mean a compound which has at least about10 units of the formula (1). The polymers, oligomers or dendrimers maybe conjugated, partially conjugated or non-conjugated. The trimers,tetramers, pentamers, oligomers or polymers may be linear or branched.In the line-arly linked structures, the units of the formula (1) can belinked directly to one another or linked to one another via a divalentgroup, for example via a substituted or unsubstituted alkylene group,via a heteroatom or via a divalent aromatic or heteroaromatic group. Inbranched structures, for example, three or more units of the formula (1)may be linked via a trivalent or polyvalent group, for example via atrivalent or polyvalent aromatic or heteroaromatic group, to give abranched trimer, tetramer, pentamer, oligomer or polymer.

For the recurring units of the formula (1) in dimers, trimers,tetramers, pentamers, oligomers and polymers, the same preferences applyas described above. Preferred recurring units are therefore again theunits of the formulae given above.

For the preparation of the oligomers or polymers, the monomers accordingto the invention are homopolymerised or copolymerised with furthermonomers. Suitable and preferred comonomers are selected from fluorenes(for example in accordance with EP 842208 or WO 00/22026),spirobifluor-enes (for example in accordance with EP 707020, EP 894107or WO 06/061181), para-phenylenes (for example in accordance with WO92/18552), carbazoles (for example in accordance with WO 04/070772 or WO04/113468), thiophenes (for example in accordance with EP 1028136),dihydrophenanthrenes (for example in accordance with WO 05/014689), cis-and trans-indenofluorenes (for example in accordance with WO 04/041901or WO 04/113412), ketones (for example in accordance with WO 05/040302),phenanthrenes (for example in accordance with WO 05/104264 or WO07/017066) or also a plurality of these units. The polymers, oligomersand dendrimers usually also contain further units, for example emitting(fluorescent or phosphorescent) units, such as, for example,vinyltriarylamines (for example in accordance with WO 07/068325) orphosphorescent metal complexes (for example in accordance with WO06/003000), and/or charge-transport units. The recurring units accordingto the invention are particularly suitable as charge-transport units forelectrons.

The present invention furthermore relates to mixtures comprising atleast one compound of the formula (1) or a corresponding dimer, trimer,tetramer, pentamer, oligomer or polymer and at least one furthercompound. The further compound can be, for example, a fluorescent orphosphorescent dopant if the compound of the formula (1) is used asmatrix material. Suitable fluorescent and phosphorescent dopants arementioned below in connection with the organic electroluminescentdevices and are also preferred for the mixtures according to theinvention. The further compound can also be a dopant if the compound ofthe formula (1) is a hole-transport or electron-transport compound.Suitable dopants are mentioned below in connection with the organicelectroluminescent devices.

For processing from solution or the liquid phase, for example by spincoating or by printing processes, solutions or formulations of thecompounds of the formula (1) are necessary. It may also be preferred touse mixtures of two or more solvents. Suitable and preferred solventsare, for example, toluene, anisole, o-, m- or p-xylene, methyl benzoate,dimethylanisole, mesitylene, tetralin, veratrol, THF, methyl-THF, THP,chlorobenzene, dioxane or mixtures of these solvents.

The present invention therefore furthermore relates to a formulationcomprising at least one compound of the formula (1) and one or moresolvents, in particular organic solvents. These are preferablysolutions, suspensions or mini emulsions, in particular solutions. Theway in which solutions of this type can be prepared is known to theperson skilled in the art and is described, for example, in WO02/072714, WO 03/019694 and the literature cited therein.

The compounds of the formula (1) according to the invention andcorresponding dimers, trimers, tetramers, pentamers, oligomers, polymersor dendrimers are suitable for use in electronic devices, in particularin organic electroluminescent devices (OLEDs, PLEDs). Depending on thesubstitution, the compounds are employed in different functions andlayers. The preferred embodiments here conform to the formulae givenabove.

The invention therefore furthermore relates to the use of compounds ofthe formula (1) or corresponding dimers, trimers, tetramers, pentamers,oligomers, polymers or dendrimers in electronic devices, in particularin organic electroluminescent devices.

The invention still furthermore relates to electronic devices comprisingat least one compound of the formula (1) or a corresponding dimer,trimer, tetramer, pentamer, oligomer, polymer or dendrimer. Theelectronic device here is preferably selected from the group consistingof organic electroluminescent devices (OLEDs, PLEDs), organicfield-effect transistors (O-FETs), organic thin-film transistors(O-TFTs), organic light-emitting transistors (O-LETs), organicintegrated circuits (O-ICs), organic solar cells (O-SCs), organicfield-quench devices (O-FQDs), light-emitting electrochemical cells(LECs), organic laser diodes (O-lasers) or organic photoreceptors.

Particular preference is given to organic electroluminescent devicescomprising an anode, a cathode and at least one emitting layer,characterised in that at least one organic layer, which may be anemitting layer or another layer, comprises at least one compound of theformula (1) or a corresponding dimer, trimer, tetramer, pentamer,oligomer, polymer or dendrimer.

The cathode preferably comprises metals having a low work function,metal alloys or multilayered structures comprising various metals, suchas, for example, alkaline-earth metals, alkali metals, main-group metalsor lanthanoids (for example Ca, Ba, Mg, Al, In, Mg, Yb, Sm, etc.). Inthe case of multilayered structures, further metals which have arelatively high work function, such as, for example, Ag, can also beused in addition to the said metals, in which case combinations of themetals, such as, for example, Mg/Ag, Ca/Ag or Ba/Ag, are generally used.Preference is likewise given to metal alloys, in particular alloyscomprising an alkali metal or alkaline-earth metal and silver,particularly preferably an alloy of Mg and Ag. It may also be preferredto introduce a thin interlayer of a material having a high dielectricconstant between a metallic cathode and the organic semicon-ductor.Suitable for this purpose are, for example, alkali-metal oralkaline-earth metal fluorides, but also the corresponding oxides orcarbonates (for example LiF, Li₂, CsF, Cs₂CO₃, BaF₂, MgO, NaF, etc.).Organic metal compounds, such as, for example, lithium quinolinate, canalso be used. The layer thickness of this layer is preferably between0.5 and 5 nm.

The anode preferably comprises materials having a high work function.The anode preferably has a work function of greater than 4.5 eV againstvacuum. Suitable for this purpose are on the one hand metals having ahigh redox potential, such as, for example, Ag, Pt or Au. On the otherhand, metal/metal oxide electrodes (for example Al/Ni/NiO_(x),Al/PtO_(x)) may also be preferred. For some applications, at least oneof the electrodes must be transparent or partially transparent in orderto enable either the irradiation of the organic material (O-SCs) or thecoupling-out of light (OLEDs/PLEDs, O-lasers). Preferred anode materialsfor transparent or partially transparent anodes are conductive mixedmetal oxides. Particular preference is given to indium tin oxide (ITO)or indium zinc oxide (IZO). Preference is furthermore given toconductive, doped organic materials, in particular conductive, dopedpolymers, for example PEDOT or PANI.

Apart from the cathode, anode and emitting layer, the organicelectroluminescent device may also comprise further layers. These areselected, for example, from in each case one or more hole-injectionlayers, hole-transport layers, hole-blocking layers, electron-transportlayers, electron-injection layers, electron-blocking layers,exciton-blocking layers, charge-gen-eration layers and/or organic orinorganic p/n junctions. Furthermore, the layers, in particular thecharge-transport layers, may also be doped. The doping of the layers maybe advantageous for improved charge transport. However, it should bepointed out that each of these layers does not necessarily have to bepresent, and the choice of layers is always dependent on the compoundsused and in particular also on whether the electroluminescent device isfluorescent or phosphorescent.

In a further preferred embodiment of the invention, the organicelectroluminescent device comprises a plurality of emitting layers,where at least one organic layer comprises at least one compound of theformula (1). These emission layers particularly preferably have in totala plurality of emission maxima between 380 nm and 750 nm, resultingoverall in white emission, i.e. various emitting compounds which areable to fluoresce or phospho-resce and which emit blue and yellow,orange or red light are used in the emitting layers. Particularpreference is given to three-layer systems, i.e. systems having threeemitting layers, where at least one of these layers comprises at leastone compound of the formula (1) and where the three layers exhibit blue,green and orange or red emission (for the basic structure, see, forexample, WO 05/011013). Emitters which have broad-band emission bandsand thus exhibit white emission are likewise suitable for whiteemission. For white-emitting electroluminescent devices, it is likewisepreferred for one or more emitting layers to be phosphorescent and oneor more emitting layers to be fluorescent.

In a preferred embodiment of the invention, the compounds of the formula(1) are employed as matrix material for fluorescent or phosphorescentcompounds in an emitting layer, in particular as matrix material forphosphorescent compounds.

A matrix material in a system comprising matrix and dopant is taken tomean the component which is present in the higher proportion in thesystem. In a system comprising a matrix and a plurality of dopants, thematrix is taken to mean the component whose proportion in the mixture isthe highest.

In an embodiment, the compound of the formula (1) is employed as theonly matrix material in the mixture with the emitter. In a furtherembodiment of the invention, the compound of the formula (1) is employedas a mixture together with a further matrix material and an emitter.Preferably, one component of this mixture of matrix materials is ahole-transport compound and the other is an electron-transport compoundof the formula (1).

Suitable materials with which the compound of the formula (1) can beemployed as a mixture are selected from the group consisting of aromaticketones, aromatic phosphine oxides or aromatic sulfoxides or sulfones,for example in accordance with WO 04/013080, WO 04/093207, WO 06/005627or WO 2010/006680, triarylamines, carbazole derivatives, for example CBP(N,N-biscarbazolylbiphenyl), mCBP or the carbazole derivatives disclosedin WO 05/039246, US 2005/0069729, JP 2004/288381, EP 1205527 or WO08/086851, indolocarbazole derivatives, for example in accordance withWO 07/063754 or WO 08/056746, indenocarbazole derivatives, for examplein accordance with the unpublished applications DE 102009023155.2 or DE102009031021.5, azacarbazole derivatives, for example in accordance withEP 1617710, EP 1617711, EP 1731584, JP 2005/347160, bipolar matrixmaterials, for example in accordance with WO 07/137725, silanes, forexample in accordance with WO 05/111172, azaboroles or boronic esters,for example in accordance with WO 06/117052, triazine derivatives, forexample in accordance with WO 2010/015306, WO 07/063754 or WO 08/056746,zinc complexes, for example in accordance with EP 652273 or WO09/062578, diazasilole or tetraazasilole derivatives, for example inaccordance with WO 2010/054729, diazaphosphole derivatives, for examplein accordance with WO 2010/054730, or bridged carbazole derivatives, forexample in accordance with US 2009/0136779 or the unpublishedapplication DE 102009048791.3. A further phosphorescent emitter whichemits at shorter wavelength than the actual emitter may likewise bepresent in the mixture as co-host. It is furthermore possible to usemixtures of two or more compounds of the formula (1) as matrixmaterials.

If the compound of the formula (1) is employed as matrix material for anemitting compound in an emitting layer, it can be employed incombination with one or more phosphorescent materials (tripletemitters). Phosphores-cence in the sense of this invention is taken tomean the luminescence from an excited state of relatively high spinmultiplicity, i.e. a spin state>1, in particular from an excited tripletstate. For the purposes of this invention, all luminescenttransition-metal complexes and all luminescent lanthanide complexes, inparticular luminescent iridium, platinum, osmium, gold and coppercompounds, are referred to as phosphorescent materials. The mixture ofthe compound of the formula (1) and the emitting compound then comprisesbetween 99 and 1% by weight, preferably between 98 and 10% by weight,particularly preferably between 97 and 60% by weight, in particularbetween 95 and 75% by weight, of the compound of the formula (1), basedon the entire mixture of emitter and matrix material. Correspondingly,the mixture comprises between 1 and 99% by weight, preferably between 2and 90% by weight, particularly preferably between 3 and 40% by weight,in particular between 5 and 25% by weight, of the emitter, based on theentire mixture of emitter and matrix material.

Suitable phosphorescent compounds (=triplet emitters) are, inparticular, compounds which emit light, preferably in the visibleregion, on suitable excitation and in addition contain at least one atomhaving an atomic number of greater than 20, preferably greater than 38and less than 84, particularly preferably greater than 56 and less than80. The phosphores-cence emitters used are preferably compounds whichcontain copper, molybdenum, tungsten, rhenium, ruthenium, osmium,rhodium, iridium, palladium, platinum, silver, gold or europium, inparticular compounds which contain iridium or platinum.

Examples of the emitters described above are revealed by theapplications WO 00/70655, WO 01/41512, WO 02/02714, WO 02/15645, EP1191613, EP 1191612, EP 1191614, WO 05/033244, WO 05/019373, US2005/0258742, WO 09/146770, WO 10/015307, WO 10/031485, WO 10/054731 andWO 10/054728. Furthermore suitable are the complexes in accordance withthe unpublished applications DE 102009007038.9, DE 102009011223.5 and DE102009013041.1. In general, all phosphorescent complexes as used inaccordance with the prior art for phosphorescent OLEDs and as are knownto the person skilled in the art in the area of organicelectroluminescence are suitable, and the person skilled in the art willbe able to use further phosphorescent complexes without inventive step.

If the compound of the formula (1) is employed as matrix material forfluorescent compounds, the proportion of the matrix material in theemitting layer is between 50.0 and 99.9% by weight, preferably between80.0 and 99.5% by weight, particularly preferably between 90.0 and 99.0%by weight. Correspondingly, the proportion of the dopant is between 0.1and 50.0% by weight, preferably between 0.1 and 20.0% by weight,particularly preferably between 0.5 and 15% by weight, very particularlypreferably between 1.0 and 10.0% by weight.

Preferred dopants are selected from the class of the monostyrylamines,the distyrylamines, the tristyrylamines, the tetrastyrylamines, thestyryl-phosphines, the styryl ethers and the arylamines. Amonostyrylamine is taken to mean a compound which contains onesubstituted or unsubstituted styryl group and at least one, preferablyaromatic, amine. A distyryl-amine is taken to mean a compound whichcontains two substituted or unsubstituted styryl groups and at leastone, preferably aromatic, amine. A tristyrylamine is taken to mean acompound which contains three substituted or unsubstituted styryl groupsand at least one, preferably aromatic, amine. A tetrastyrylamine istaken to mean a compound which contains four substituted orunsubstituted styryl groups and at least one, preferably aromatic,amine. The styryl groups are particularly preferably stilbenes, whichmay also be further substituted. Corresponding phosphines and ethers aredefined analogously to the amines. An arylamine or aromatic amine in thesense of this invention is taken to mean a compound which contains threesubstituted or unsubstituted aromatic or heteroaromatic ring systemsbonded directly to the nitrogen. At least one of these aromatic orheteroaromatic ring systems is preferably a condensed ring system,preferably having at least 14 aromatic ring atoms. Preferred examplesthereof are aromatic anthracenamines, aromatic anthracenediamines,aromatic pyrenamines, aromatic pyrenediamines, aromatic chrysenamines oraromatic chrysenediamines. An aromatic anthracenamine is taken to mean acompound in which one diarylamino group is bonded directly to ananthracene group, preferably in the 9-position. An aromaticanthracenediamine is taken to mean a compound in which two diarylaminogroups are bonded directly to an anthracene group, preferably in the9,10-position. Aromatic pyrenamines, pyrenediamines, chrysenamines andchrysenediamines are defined analogously thereto, where the diarylaminogroups on the pyrene are preferably bonded in the 1-position or in the1,6-position. Further preferred dopants are selected fromindenofluorenamines or indenofluorenediamines, for example in accordancewith WO 06/122630, benzoindeno-fluorenamines orbenzoindenofluorenediamines, for example in accordance with WO08/006449, and dibenzoindenofluorenamines ordibenzo-indenofluorenediamines, for example in accordance with WO07/140847. Examples of dopants from the class of the styrylamines aresubstituted or unsubstituted tristilbenamines or the dopants describedin WO 06/000388, WO 06/058737, WO 06/000389, WO 07/065549 and WO07/115610. Further suitable fluorescent dopants are the condensedaromatic hydro-carbons disclosed in WO 2010/012328.

In still a further embodiment of the invention, the compounds of theformula (1) are employed as electron-transport material or ashole-blocking material in an electron-transport layer or hole-blockinglayer. Due to the presence of the electron-deficient heteroaromaticgroups R¹ and/or R², these compounds have very good electron-transportproperties. It may furthermore be preferred for the compound to be dopedwith electron-donor compounds. A hole-blocking layer in the sense ofthis invention is a layer which is located between an emitting layer andan electron-transport layer and is directly adjacent to the emittinglayer. If the compound of the formula (1) is employed aselectron-transport material, it may be preferred to employ this as amixture with a further compound. Preferred mixture components arealkali-metal compounds, preferably lithium compounds, particularlypreferably Liq (lithium quinolinate) or Liq derivatives.

In a further embodiment of the invention, the compounds of the formula(1) are employed as hole-transport material or as hole-injectionmaterial or as electron-blocking material or as exciton-blockingmaterial. Preferred groups which improve hole transport are, forexample, the groups N(R¹), S or O, in particular N(R¹), as bridge Y orelectron-rich heteroaromatic groups, in particular thiophene, pyrrole orfuran, as group R¹. The compound is preferably employed in ahole-transport or hole-injection or elec-tron-blocking orexciton-blocking layer. A hole-injection layer in the sense of thisinvention is a layer which is directly adjacent to the anode. Ahole-transport layer in the sense of this invention is a layer which islocated between a hole-injection layer and an emission layer. Anelectron-blocking or exciton-blocking layer in the sense of thisinvention is a layer which is directly adjacent to an emitting layer onthe anode side. If the compounds of the formula (1) are used ashole-transport or hole-injection material, it may be preferred for themto be doped with electron-acceptor compounds, for example with F₄-TCNQor with compounds as described in EP 1476881 or EP 1596445.

Recurring units of the formula (1) can also be employed in polymers,either as polymer backbone, as hole-transporting unit and/or aselectron-transporting unit. The preferred substitution patterns herecorrespond to those described above.

Preference is furthermore given to an organic electroluminescent device,characterised in that one or more layers are applied by means of asublimation process, in which the materials are vapour-deposited invacuum sublimation units at a pressure of less than 10⁻⁵ mbar,preferably less than 10⁻⁶ mbar. However, it should be noted that thepressure may also be even lower, for example less than 10⁻⁷ mbar.

Preference is likewise given to an organic electroluminescent device,characterised in that one or more layers are applied by means of theOVPD (organic vapour phase deposition) process or with the aid ofcarrier-gas sublimation, in which the materials are applied at apressure between 10⁻⁵ mbar and 1 bar. A special case of this process isthe OVJP (organic vapour jet printing) process, in which the materialsare applied directly through a nozzle and thus structured (for exampleM. S. Arnold et al., Appl. Phys. Lett. 2008, 92, 053301).

Preference is furthermore given to an organic electroluminescent device,characterised in that one or more layers are produced from solution,such as, for example, by spin coating, or by means of any desiredprinting process, such as, for example, LITI (light induced thermalimaging, thermal transfer printing, ink-jet printing, screen printing,flexographic printing, off-set printing or nozzle printing. Solublecompounds are necessary for this purpose. High solubility can beachieved through suitable substitution of the compounds. It is possiblehere to apply not only solutions of individual materials, but alsosolutions which comprise a plurality of compounds, for example matrixmaterial and dopant.

The organic electroluminescent device may also be produced as a hybridsystem by applying one or more layers from solution and applying one ormore other layers by vapour deposition. Thus, for example, it ispossible to apply an emitting layer comprising a compound of the formula(1) and a phosphorescent dopant from solution and to apply ahole-blocking layer and/or an electron-transport layer on top by vacuumvapour deposition. The emitting layer comprising a compound of theformula (1) and a phosphorescent dopant can likewise be applied byvacuum vapour deposition, and one or more other layers can be appliedfrom solution. Alternatively or additionally, it is, for example, alsopossible to apply an emitting layer from solution and to apply anelectron-transport layer comprising a compound of the formula (1),optionally in combination with an organic alkali-metal compound, on topby vacuum vapour deposition.

These processes are generally known to the person skilled in the art andcan be applied by him without problems to organic electroluminescentdevices comprising compounds of the formula (1) or the preferredembodiments mentioned above.

The compounds according to the invention have the following surprisingadvantages over the prior art on use in organic electroluminescentdevices:

-   -   1. The compounds according to the invention have high thermal        stability.    -   2. The compounds according to the invention have high solubility        in com-mon organic solvents and very good film-formation        properties and are therefore particularly highly suitable for        processing from solution.    -   3. The OLEDs produced using the compounds according to the        invention generally have a very long lifetime.    -   4. The OLEDs produced using the compounds according to the        invention generally have very high quantum efficiency.

The invention is described in greater detail by the following exampleswithout wishing it to be restricted thereby. The person skilled in theart will be able, without being inventive, to prepare further compoundsaccording to the invention and to use them in electronic devices andwill thus be able to carry out the invention throughout the rangeclaimed.

EXAMPLES

The following syntheses are carried out, unless indicated otherwise,under a protective-gas atmosphere in dried solvents. Starting material 8and solvents are commercially available, for example from ALDRICH.Compounds 1 and 5 can be prepared in accordance with WO 09/124627.Compound 2 can be prepared analogously to J. Mater. Chem. 2007, 17,3714-3719.

Example 1: Preparation of Compound 4

a) Preparation of Compound 3:

850 ml of dimethyl sulfoxide, 25.18 g (1.1 molar equivalents, 0.099 mol)of bis(pinacolato)diborane and 25.66 g (2.9 molar equivalents, 0.261mol) of potassium acetate are added to 35.0 g (1 molar equivalent, 0.090mol) of compound 2. 2.25 g (3 mmol) of1,1-bis(diphenylphosphino)ferrocene-pal-ladium(II) chloride (complexwith dichloromethane (1:1), Pd 13%) are sub-sequently added. The batchis heated at 100° C. for 3 h, then cooled to room temperature, and 400ml of water are added. The mixture is extracted with ethyl acetate, andthe combined organic phases are then dried over sodium sulfate andevaporated under reduced pressure. Purification is carried out byrecrystallisation (heptane) and gives a beige solid (81.3%).

b) Preparation of Compound 4:

10.97 g (1 molar equivalent, 0.017 mol) of compound 1, 33.14 g (4.4molar equivalents, 0.076 mol) of compound 3 and 29.42 g (8.0 molarequivalents, 0.139 mol) of tripotassium phosphate are suspended in 250ml of toluene, 125 ml of dioxane and 325 ml of water. 1.270 g (4.2 mmol)of tri-o-tolylphosphine and then 0.156 g (0.7 mmol) of palladium(II)acetate are added to this suspension, and the reaction mixture is heatedunder reflux for 40 h. After cooling, the organic phase is separatedoff. The aqueous phase is extracted with dichloromethane, and thecombined organic phases are then dried over sodium sulfate, filtered andevaporated under reduced pressure. The residue is recrystallised fromdimethylformamide and extracted with hot toluene. The yield is 9.4 g(6.1 mmol), corresponding to 35.1% of theory.

Example 2: Preparation of Compound 9

a) Preparation of Compound 6:

20 g (32.1 mmol) of compound 5 are suspended in 10 ml of chloroform and50 ml of glacial acetic acid with 3.4 g (19.2 mmol) of iodic acid and4.9,g (19.2 mmol) of iodine, and the mixture is heated at 80° C. After aTLC check, the batch is cooled to room temperature and 250 ml of waterare added. The mixture is extracted with methylene chloride, and thecombined organic phases are then dried using sodium sulfate, filteredand evaporated under reduced pressure. Purification is carried out bywashing (ethanol) and recrystallisation (toluene/ethyl acetate) andgives a colourless solid (15.3 g; 64% of theory).

b) Preparation of Compound 7:

The synthesis of compound 7 is carried out analogously to that ofcompound 3. The yield is 7.0 g (9.2 mmol), corresponding to 46% oftheory.

c) Preparation of Compound 9:

The synthesis of compound 9 is carried out analogously to that ofcompound 4. The yield is 4.48 g (5.2 mmol), corresponding to 57% oftheory.

Example 3: Preparation of Compound 11

a) Preparation of Compound 10:

The synthesis of compound 10 is carried out analogously to that ofcompound 1. 79.8 g (91.9% of theory) of a solid are obtained.

b) Preparation of Compound 11:

10.0 g (1 molar equivalent, 21 mmol) of compound 10, 20.1 g (2.2 molarequivalents, 46 mmol) of compound 3 and 53.3 g (11.9 molar equivalents,251 mmol) of tripotassium phosphate are suspended in 200 ml of toluene,200 ml of dioxane and 200 ml of water. This mixture is degassed usingargon for 15 min, and 458 mg (1.50 mmol) of tri-o-tolylphosphine andthen 230 mg (1.03 mmol) of palladium(II) acetate are then added. Thereaction mixture is heated under reflux for 16 h, during which a whiteprecipitate deposits. After cooling, 0.60 l of water and 1 l ofdichloromethane are added, and the organic phase is separated off. Theorganic phase is extracted three times with water. The combined organicphases are freed from solvents under reduced pressure. The residueobtained is stirred with 200 ml of hot ethanol, filtered off withsuction and washed with further ethanol, leaving a virtually colourlesssolid. Recrystallisation from dioxane gives 1.90 g (2.04 mmol, 96.5% oftheory) of a colourless solid.

Example 4: Preparation of Compound 15

a) Preparation of Compound 12:

The synthesis of compound 12 is carried out analogously to that ofcompound 3. The yield is 590 mg (1.04 mmol), corresponding to 25% oftheory.

b) Preparation of Compound 14:

The synthesis of compound 14 is carried out analogously to that ofcompound 8. 6.80 g (9.39 mmol, 27% of theory) of a beige solid areobtained.

c) Preparation of Compound 15:

The synthesis of compound 15 is carried out analogously to that ofcompound 11. The yield is 8.00 g (47.0 mmol), corresponding to 66% oftheory.

Example 5: Production and Characterisation of Organic ElectroluminescentDevices Comprising the Compounds According to the Invention

The structures of TEG (synthesised in accordance with WO 04/026886),TMM-1 (synthesised in accordance with DE 102008036982.9) and TMM-2(synthesised in accordance with WO 09/124627), and compounds TMM-3 to 6according to the invention are depicted below for clarity.

Materials according to the invention can be used from solution, wherethey result in significantly simpler devices which nevertheless havegood properties. The production of such components is based on theproduction of polymeric light-emitting diodes (PLEDs), which has alreadybeen described a number of times in the literature (for example in WO04/037887). In the present case, the compounds according to theinvention or likewise soluble comparative compounds (TMM-1 and TMM-2)are dissolved in toluene or chlorobenzene. The typical solids content ofsuch solutions is between 16 and 25 g/I if, as here, the layer thicknessof 80 nm which is typical for a device is to be achieved by means ofspin coating. FIG. 1 shows the typical structure of a device of thistype. Structured ITO substrates and the material for the so-calledbuffer layer (PEDOT, actually PEDOT:PSS) are commercially available (ITOfrom Technoprint and others, PEDOT:PSS as Clevios Baytron P aqueousdispersion from H.C. Starck). The interlayer used serves for holeinjection; in this case, HIL-012 from Merck is used. The emission layeris applied by spin coating in an inert-gas atmosphere, in the presentcase argon, and dried by heating at 120° C. for 10 min. Finally, acathode comprising barium and aluminium is applied by vacuum vapourdeposition. A hole-blocking layer and/or an electron-transport layer canalso be applied between the emitting layer and the cathode by vapourdeposition, and the interlayer may also be replaced by one or morelayers, which merely have to satisfy the condition that they are notdetached again by the subsequent processing step of deposition of theemitting layer from solution.

The devices are characterised by standard methods; the OLED examplesmentioned have not yet been optimised. Table 1 summarises the dataobtained. The two triplet matrix materials are present in the ratio 1:1(based on the weight of the compounds) in each of Examples 8, 13 and 14.In the case of the processed devices, it is evident here that thematerials according to the invention are superior to those previouslyavailable in terms of efficiency and/or lifetime.

The structure of the organic electroluminescent device is shown in FIG.1.

TABLE 1 Results using solution-processed materials in the deviceconfiguration of FIG. 1 Voltage Lifetime Max. [V] [h], initial EML eff.at CIE luminance Ex. 80 nm [cd/A] 100 cd/m² (x, y) 1000 cd/m² 6TMM-2:TEG  9 5.7 0.34/0.66  1200 (comp.) 7 TMM-1:TEG 14 3.8 0.35/0.68 9200 (comp.) 8 TMM-1:TMM-2: 20 3.6 0.32/0.63 12000 (comp.) TEG  9TMM-3:TEG 22 3.7 0.33/0.63 15000 10 TMM-4:TEG 23 3.5 0.33/0.63 18000 11TMM-5:TEG 29 3.6 0.34/0.62 22000 12 TMM-6:TEG 28 3.5 0.33/0.63 20000 13TMM-5:TMM-2: 33 4.5 0.34/0.62 28000 TEG 14 TMM-6:TMM-2: 32 4.2 0.33/0.6229000 TEG

1.-14. (canceled)
 15. A mixture comprising at least one compound of theformula (1) and at least one further compound

where Y is C(R¹)₂, O or NR³; X is on each occurrence, identically ordifferently, CR¹ or N, where a maximum of three groups X in each ringstand for N; A is on each occurrence, identically or differently, CR² orN, where a maximum of three groups A in each ring stand for N; R¹, R²are on each occurrence, identically or differently, H, D, Cl, Br, I, F,CN, NO₂, N(R₄)₃, Si(R⁴)₃, B(OR⁴)₂, C(═O)R⁴, P(═O)(R⁴)₂, S(═O)R⁴,S(═O)₂R⁴, —CR⁴═CR⁴—, OSO₂R⁴, a straight-chain alkyl, alkoxy orthioalkoxy group having 1 to 40 C atoms or a branched or cyclic alkyl,alkoxy or thioalkoxy group having 3 to 40 C atoms or an alkenyl oralkynyl group having 2 to 40 C atoms, each of which may be substitutedby one or more radicals R⁴, where one or more non-adjacent CH₂ groupsmay be replaced by R⁴C═CR⁴, C≡C, Si(R⁴)₂, Ge(R⁴)₂, Sn(R⁴)₂, C═O, C═S,C═Se, C═NR⁴, P(═O)(R⁴), SO, SO₂, NR⁴, O, S or CONR⁴ and where one ormore H atoms may be replaced by D, F, Cl, Br, I, CN or NO₂, or anaromatic or heteroaromatic ring system having 5 to 60 aromatic ringatoms, which may in each case be substituted by one or more radicals R⁴,or an aryloxy or heteroaryloxy group having 5 to 60 aromatic ring atoms,which may be substituted by one or more radicals R⁴, or aralkyl orheteroaralkyl group having 5 to 60 aromatic ring atoms, which may besubstituted by one or more radicals R⁴; two or more adjacentsubstituents R¹ together with the atoms to which they are bonded or twoor more adjacent substituents R² together with the atoms to which theyare bonded may also form a mono- or polycyclic, aliphatic or aromaticring system with one another; characterised in that at least one R¹which is bonded to X stands for triazine, which may be substituted byone or more radicals R⁴, or in that at least one R² stands for a6-membered heteroaromatic group, which may be substituted by one or moreradicals R⁴, and at least one radical R¹ simultaneously stands for anaromatic or heteroaromatic ring system having 5 to 60 aromatic ringatoms, which may be substituted by one or more radicals R⁴; R³ is oneach occurrence, identically or differently, an aromatic orheteroaromatic ring system having 5 to 60 ring atoms, which may in eachcase be substituted by one or more radicals R⁴, or an aryloxy orheteroaryloxy group having 5 to 60 aromatic ring atoms, which may besubstituted by one or more radicals R³, or a combination of thesesystems; R⁴ is on each occurrence, identically or differently, H, D, F,Cl, Br, I, CN, NO₂, N(R⁵)₃, Si(R⁵)₃, B(OR⁵)₂, C(═O)R⁵, P(═O)(R⁵)₂,S(═O)R⁵, S(═O)₂R⁵, —CR⁵═CR⁵—, OSO₂R⁵, a straight-chain alkyl, alkoxy orthioalkoxy group having 1 to 40 C atoms or a branched or cyclic alkyl,alkoxy or thioalkoxy group having 3 to 40 C atoms or an alkenyl oralkynyl group having 2 to 40 C atoms, each of which may be substitutedby one or more radicals R⁵, where one or more non-adjacent CH₂ groupsmay be replaced by R⁵C═CR⁵, C≡C, Si(R⁵)₂, Ge(R⁵)₂, Sn(R⁵)₂, C═O, C═S,C═Se, C═NR⁵, P(═O)(R⁵), SO, SO₂, NR⁵, O, S or CONR⁵ and where one ormore H atoms may be replaced by D, F, Cl, Br, I, CN or NO₂, or anaromatic or heteroaromatic ring system having 5 to 60 aromatic ringatoms, which may in each case be substituted by one or more radicals R⁵,or an aryloxy or heteroaryloxy group having 5 to 60 aromatic ring atoms,which may be substituted by one or more radicals R⁵, or aralkyl orheteroaralkyl group having 5 to 60 aromatic ring atoms, which may besubstituted by one or more radicals R⁵; two or more radicals R⁴ here mayalso form a mono- or polycyclic, aliphatic or aromatic ring system withone another together with the atoms to which they are bonded; R⁵ is oneach occurrence, identically or differently, an aliphatic, aromaticand/or heteroaromatic hydrocarbon radical having 1 to 20 C atoms; two ormore radicals R⁵ here may also form a mono- or polycyclic, aliphatic oraromatic ring system with one another together with the atoms to whichthey are bonded.
 16. The Mixture according to claim 15, wherein thecompound of formula (1) is selected from a compound of the formula (2),(3), (4), (5), (6), (7), (8), (9), (10), (11), (12), (13), (14) or (15):

where the symbols and indices used have the meanings indicated in claim15.
 17. The mixture according to claim 15, wherein, if at least onegroup R¹ stands for triazine, this is 1,3,5-triazine or 1,2,4-triazine,which may in each case be substituted by one or more radicals R⁴ andwhere the radicals R⁴ which are not equal to hydrogen or deuteriumpreferably stand for an aromatic or heteroaromatic ring system; or inthat, if at least one group R² stands for a 6-membered heteroaromaticgroup, this is selected from triazine, pyrimidine, pyrazine, pyridazineor pyridine, each of which may be substituted by one or more radicals R⁴and where the radicals R⁴ which are not equal to hydrogen or deuteriumpreferably stand for an aromatic or heteroaromatic ring system.
 18. Themixture according to claim 15, wherein the triazine substituents R¹ andR² and the pyrimidine substituents R² are selected from the groupsdepicted below:

where the dashed bond indicates the link from this group to theskeleton.
 19. The mixture according to claim 15, wherein the compound offormula (1) is a compound of the formula (16) or (17):


20. The mixture according to claim 15, wherein the compound of formula(1) is selected from compounds of the formulae (20), (21), (24) or (25):


21. The mixture according to claim 15, wherein the compound of formula(1) is a compound of formulae (29) or (31):


22. The mixture according to claim 15, wherein the at least one furthermaterial is a matrix material.
 23. The mixture according to claim 22,wherein the matrix material is a hole transport material.
 24. Themixture according to claim 15 further comprising a phosphorescent orfluorescent compound.
 25. A formulation comprising at least one mixtureaccording to claim 15 and one or more solvent.
 26. An electronic devicescomprising at least one mixture according to claim 15, where theelectronic device is selected from the group consisting of organicelectroluminescent devices (OLEDs, PLEDs), organic field-effecttransistors (O-FETs), organic thin-film transistors (O-TFTs), organiclight-emitting transistors (O-LETs), organic integrated circuits(O-ICs), organic solar cells (O-SCs), organic field-quench devices(O-FQDs), light-emitting electrochemical cells (LECs), organic laserdiodes (O-lasers) and organic photoreceptors.
 27. The electronic deviceof claim 26, wherein the device is an organic electroluminescent device.